/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.handler.codec.http.websocketx;

import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpHeaderValues;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpResponseStatus;
import io.netty.util.CharsetUtil;

import static io.netty.handler.codec.http.HttpVersion.*;

/**
 * <p>
 * Performs server side opening and closing handshakes for web socket
 * specification version
 * <a href="http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-10"
 * >draft-ietf-hybi-thewebsocketprotocol- 10</a>
 * </p>
 */
public class WebSocketServerHandshaker08 extends WebSocketServerHandshaker
{

    public static final String WEBSOCKET_08_ACCEPT_GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";

    private final boolean allowExtensions;

    private final boolean allowMaskMismatch;

    /**
     * Constructor specifying the destination web socket location
     *
     * @param webSocketURL URL for web socket communications. e.g
     *        "ws://myhost.com/mypath". Subsequent web socket frames will be
     *        sent to this URL.
     * @param subprotocols CSV of supported protocols
     * @param allowExtensions Allow extensions to be used in the reserved bits
     *        of the web socket frame
     * @param maxFramePayloadLength Maximum allowable frame payload length.
     *        Setting this value to your application's requirement may reduce
     *        denial of service attacks using long data frames.
     */
    public WebSocketServerHandshaker08(String webSocketURL, String subprotocols,
            boolean allowExtensions, int maxFramePayloadLength)
    {
        this(webSocketURL, subprotocols, allowExtensions, maxFramePayloadLength,
                false);
    }

    /**
     * Constructor specifying the destination web socket location
     *
     * @param webSocketURL URL for web socket communications. e.g
     *        "ws://myhost.com/mypath". Subsequent web socket frames will be
     *        sent to this URL.
     * @param subprotocols CSV of supported protocols
     * @param allowExtensions Allow extensions to be used in the reserved bits
     *        of the web socket frame
     * @param maxFramePayloadLength Maximum allowable frame payload length.
     *        Setting this value to your application's requirement may reduce
     *        denial of service attacks using long data frames.
     * @param allowMaskMismatch When set to true, frames which are not masked
     *        properly according to the standard will still be accepted.
     */
    public WebSocketServerHandshaker08(String webSocketURL, String subprotocols,
            boolean allowExtensions, int maxFramePayloadLength,
            boolean allowMaskMismatch)
    {
        super(WebSocketVersion.V08, webSocketURL, subprotocols,
                maxFramePayloadLength);
        this.allowExtensions = allowExtensions;
        this.allowMaskMismatch = allowMaskMismatch;
    }

    /**
     * <p>
     * Handle the web socket handshake for the web socket specification <a href=
     * "http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-08">HyBi
     * version 8 to 10</a>. Version 8, 9 and 10 share the same wire protocol.
     * </p>
     *
     * <p>
     * Browser request to the server:
     * </p>
     *
     * <pre>
     * GET /chat HTTP/1.1
     * Host: server.example.com
     * Upgrade: websocket
     * Connection: Upgrade
     * Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
     * Sec-WebSocket-Origin: http://example.com
     * Sec-WebSocket-Protocol: chat, superchat
     * Sec-WebSocket-Version: 8
     * </pre>
     *
     * <p>
     * Server response:
     * </p>
     *
     * <pre>
     * HTTP/1.1 101 Switching Protocols
     * Upgrade: websocket
     * Connection: Upgrade
     * Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
     * Sec-WebSocket-Protocol: chat
     * </pre>
     */
    @Override
    protected FullHttpResponse newHandshakeResponse(FullHttpRequest req,
            HttpHeaders headers)
    {
        FullHttpResponse res = new DefaultFullHttpResponse(HTTP_1_1,
                HttpResponseStatus.SWITCHING_PROTOCOLS);

        if (headers != null)
        {
            res.headers().add(headers);
        }

        CharSequence key = req.headers().get(HttpHeaderNames.SEC_WEBSOCKET_KEY);
        if (key == null)
        {
            throw new WebSocketHandshakeException(
                    "not a WebSocket request: missing key");
        }
        String acceptSeed = key + WEBSOCKET_08_ACCEPT_GUID;
        byte[] sha1 = WebSocketUtil
                .sha1(acceptSeed.getBytes(CharsetUtil.US_ASCII));
        String accept = WebSocketUtil.base64(sha1);

        if (logger.isDebugEnabled())
        {
            logger.debug(
                    "WebSocket version 08 server handshake key: {}, response: {}",
                    key, accept);
        }

        res.headers().add(HttpHeaderNames.UPGRADE, HttpHeaderValues.WEBSOCKET);
        res.headers().add(HttpHeaderNames.CONNECTION, HttpHeaderValues.UPGRADE);
        res.headers().add(HttpHeaderNames.SEC_WEBSOCKET_ACCEPT, accept);

        String subprotocols = req.headers()
                .get(HttpHeaderNames.SEC_WEBSOCKET_PROTOCOL);
        if (subprotocols != null)
        {
            String selectedSubprotocol = selectSubprotocol(subprotocols);
            if (selectedSubprotocol == null)
            {
                if (logger.isDebugEnabled())
                {
                    logger.debug("Requested subprotocol(s) not supported: {}",
                            subprotocols);
                }
            }
            else
            {
                res.headers().add(HttpHeaderNames.SEC_WEBSOCKET_PROTOCOL,
                        selectedSubprotocol);
            }
        }
        return res;
    }

    @Override
    protected WebSocketFrameDecoder newWebsocketDecoder()
    {
        return new WebSocket08FrameDecoder(true, allowExtensions,
                maxFramePayloadLength(), allowMaskMismatch);
    }

    @Override
    protected WebSocketFrameEncoder newWebSocketEncoder()
    {
        return new WebSocket08FrameEncoder(false);
    }
}
